This invention relates to an improved tube-to-tube welding head.
A typical tube-to-tube welding head for joining two tubes positioned end-to-end includes a welding electrode, which is rotated around the joint between the tubes and a pair of clamps for holding the tubes in the correct position with respect to each other and the welding electrode. The clamps include a fixed member, a rotatable member and a hinge to permit the rotatable member to be moved clear of the tubes when the tubes are either inserted into or removed from the welding head. One such device is shown in U.S. Pat. No. 5,220,144.
When welding large diameter tubes, such as tubes up to five inches in diameter, the welding operation takes considerable time, up to four or five minutes, and as a consequence, the entire welding head becomes hot, 300.degree. F. to 400.degree. F. or higher. Once the welding operation is completed, the clamps are released, and the welding head is removed from the now joined tubes. Because the welding head is so hot, however, the operator must wear gloves to handle the release of the clamps and the installation of the welding head and closure of the clamps on the next pair of tubes to be welded.
In one prior art device, the clamp members are provided with passages through which cooling fluid was passed to reduce the temperature. Cooling of the clamp members can bring their temperature down considerably, from ambient to approximately 140.degree. F. In that device, the cooling passages of the rotatable member were connected by flexible hoses to the fixed components of the welding head. External hoses in the vicinity of the hinge necessarily extended outwardly from the welding head and thus were in the way of a smooth and efficient operation, especially in confined spaces. Further, exposed hoses are subject to breaking or damage.